Automatic gain control circuits utilizing digital feedback are known in the prior art. In particular, such automatic gain control circuits utilizing digital feedback are advantageously used to replace various analog feedback control techniques that have previously been used with random stroke deflection signal generation in video displays to correct for system transmission losses between a display signal generator and a remote video display. With these prior art analog feedback techniques the feedback signal itself is subject to transmission losses that limit the effectiveness of such analog techniques and has led to the use of automatic gain control circuits with digital feedback in the remote display applications to increase the display resolution and accuracy. The number of discrete control levels available to a digital display generator is primarily limited to the binary bit size of the binary words that can be generated thereby. For example, a digital display generator using a processor utilizing an eight bit binary word can only identify two hundred fifty-six different discrete control levels as is known by those skilled in the art.
Very often it is desired to specify more discrete control levels than can normally be addressed by a given word bit size, and in particular in the use of a display generator or processor for testing of video display systems. In the test mode it may be desirable to make differential or relative type measurements thereby requiring resolution capabilities greater than would normally be needed for that display processor. A prior art solution to this problem is for a display processor to make an address up of two binary words sequentially generated. However, this approach introduces much complexity into the equipment and computer programs and slows the microprocessor down since it must spend more time generating, transmitting and receiving two part addresses and to control other equipment to do so. This is totally unacceptable in a display processor application where signal generation must be accomplished in real time.
Thus, there is a need in the art for a method and equipment for providing an automatic gain control circuit using digital feedback that can increase display resolution and accuracy beyond that normally obtainable with a display processor having a given bit word size without using multiple-part addressing.